1. Field of the Invention
The present invention relates to an evaporator unit having a plurality of heat exchangers, and an ejector type refrigeration cycle, in which the evaporator unit is used.
2. Description of Related Art
U.S. 2005/0268644 A1 (corresponding to JP-A-2005-308384) discloses an ejector type refrigeration cycle, in which air is cooled by an upwind side heat exchanger located at the upwind side of an air flow, and the air cooled by the upwind side heat exchanger is further cooled by a downwind side heat exchanger located at the downwind side of the air flow.
The upwind side heat exchanger is connected to a diffuser of an ejector, and the downwind side heat exchanger is connected to a refrigerant suction port of the ejector. A refrigerant evaporation temperature in the upwind side heat exchanger is made higher than a refrigerant evaporation temperature in the downwind side heat exchanger by a pressure-increasing operation of the diffuser. Thereby, a difference between an air temperature and a refrigerant evaporation temperature can be secured in each of the upwind side heat exchanger and the downwind side heat exchanger. Thus, the air can be effectively cooled.
WO 2006/109617 proposes an ejector type refrigeration cycle device, in which an upwind side heat exchanger, a downwind side heat exchanger and an ejector are integrated. The ejector is located inside of a header tank in the downwind side heat exchanger.
Because the ejector is integrally formed inside of the downwind side heat exchanger, the downwind side heat exchanger and the ejector can be easily and accurately mounted to the device. Further, because a refrigerant suction port of the ejector is directly open to a refrigerant gathering part of the header tank, pressure loss can be reduced when refrigerant is drawn into the ejector through the suction port from the downwind side heat exchanger.
However, when the device is actuated, temperature distribution for air flowing out of the downwind side heat exchanger may not be uniform. This is because a refrigerant superheat area of the upwind side heat exchanger and a refrigerant superheat area of the downwind side heat exchanger may be overlapped with each other in a direction of the air flow.
Because refrigerant is in a gas phase in the refrigerant superheat areas, the refrigerant absorbs only sensible heat from the air flow. That is, the air flow is not sufficiently cooled in the refrigerant superheat areas. Therefore, when air passes through the overlapped refrigerant superheat areas, the air may not be sufficiently cooled in the heat exchangers.